1. Field of the Invention
The present invention relates generally to devices and methods for analyzing biological fluids. In particular, it relates to the design and use of centrifugal rotors which allow mixing a fluid with a reagent and delivery of that mixture to a chamber in the rotor.
Tests on blood plasma and other biological tests frequently require quick mixing of samples and reagents, and quick delivery of the resulting mixture from one portion of the rotor to another for analysis. The analysis may be a variety of optical, biological, or chemical tests or assays.
It is frequently desirable to separate cellular components from the liquid fraction of biological material prior to testing because the cellular component can interfere with certain analyses. Typically, centrifugation separates the biological material into cellular and fluid fractions. For instance, centrifugation separates whole blood into cells and plasma.
Subsequently, predetermined volumes of plasma are transferred to separate test wells by manual or automated methods. Additionally, various reagents are generally required. Usually precise quantities of these reagents must be mixed with plasma or other biological fluids. Because these procedures are labor intensive and time-consuming, assorted automated systems and methods have been proposed to more efficiently provide reagent mixing and fluid transfer to various vessels suitable for testing.
Of particular interest to the present invention are centrifugal rotors which have been modified to mix a biological fluid with an appropriate reagent or diluent. These rotors may additionally include modifications for separation of fluid from cellular components. Furthermore, appropriate alterations may permit transfer of fluid from one vessel to another. Finally, such rotors may provide a plurality of discrete test wells to facilitate testing or evaluation.
Prior art rotors have frequently utilized complex designs which are costly and difficult to manufacture. Often, the rotors require various separable parts which are brought together or separated at different points in the centrifugation procedure. Previous centrifugal rotors have often been limited in the number of discrete samples and test wells which they can provide. In some cases, these rotors require use of a separate displacement fluid to effect flow of blood and plasma through the system.
For these reasons, it would be desirable to provide improved centrifugal rotors and methods suitable for quickly and easily mixing a volume of fluid with a reagent, and for transferring the resulting mixture from its mixing vessel to another chamber. The fluid could be transferred, for example, into chambers suitable for separation of cellular components and ultimately distributed into test wells for analysis within the rotor. Additionally, the rotors should be capable of mixing and distributing relatively small volumes of fluid.
The rotors should be able to accommodate relatively large numbers of test wells or cuvettes, and the rotor design should be simple and amenable to low-cost manufacture. It would be particularly desirable if the rotors were of unitary construction with no separable or movable parts. Liquid mixing methods should be simple and performable in relatively short times. The methods should require relatively few steps and minimal human intervention. It would be advantageous if the methods required only rotation of the rotor in order to effect mixing and delivery of the fluid.
2. Description of the Background Art
U.S. Pat. No. 4,894,204 to Cornut discloses a centrifugal rotor having a calibration vessel connected to an overflow vessel. The calibration vessel has a feed orifice through which it communicates with a central receptacle and an exit orifice located in the wall opposite the feed orifice. The exit orifice is designed such that liquid begins to escape from the calibration vessel from the start of its being filled.
U.S. Pat. No. 4,898,832 to Klose describes a rotor which includes dried reagents adsorbed or bound to a solid carrier. A sample solution is moved along the rotor by use of centrifugal force and/or pressure force.
U.S. Pat. No. 3,829,223 to Hamel discloses a rotor adapted for mixing sample and reagent for photometric analysis in the rotor. Ramp-like projections on the walls of the test wells assist with mixing.
U.S. Pat. No. 3,795,451 to Mailen teaches a rotor for mixing a sample and reagent using a variation in rotational speed to provide mixing. A capillary passage is fed at increased rotational speeds to transfer the liquid as flow over a steep angle is permitted.
U.S. Pat. No. 3,873,217 to Anderson describes a rotor for photometric analysis using static loading of a main cavity and distribution of liquid to cuvettes using dynamic loading caused by rotational forces.
U.S. Pat. No. 4,387,164 to Hevey relates to chemical analyses of assay mediums and describes using reagents dispersed in soluble film.
U.S. Pat. No. 3,881,827 to Gilford teaches an apparatus and chamber for measuring cardiac output and includes a chamber for mixing a precise amount of dye with blood.
U.S. Pat. No. 4,225,558 to Peterson discloses a fluid test apparatus for multiple fluid samples. A sample and reagent are held in separate chambers until centrifugal force provides migration of the two fluids to a common chamber.
U.S. Pat. No. 3,864,089 describes a rotor for blood fractionation. U.S. Pat. No. 4,279,862 to Bretaudiere is directed to a rotor which has means for creating a pressure differential and/or turbulence to produce a homogeneous mixture of reagent and sample. U.S. Pat. No. 4,509,856 is directed to a rotor useful for photometric analysis of a sample. U.S. Pat. No. 4,515,889 relates to the rotor having a plurality of interconnected small hollow spaces adapted for mixing reaction components. U.S. Pat. No. 4,689,203 relates to a centrifugal rotor designed for separating blood plasma from red and white blood cells.
The following U.S. patents relate to rotors providing measurement of a predetermined volume as the rotor spins. U.S. Pat. No. 3,899,296 to Mailen describes a rotor for whole blood samples in which the cellular component is separated from the plasma and measured subvolumes of the plasma are distributed to sample analysis cuvettes. Delivery of the measured volumes is obtained by applying a slight positive air pressure to the passageways containing the plasma. U.S. Pat. No. 4,469,793 relates to centrifugal rotor having a measurement chamber having inlet and outlet orifices. The outlet orifice leads to passages which carry liquid to an overflow chamber when the rotor is rotating in a first direction and to a receptor cell when the rotor is rotating in a second, opposite direction. U.S. Pat. No. 4,284,602 describes a rotor which uses a heavy displacement fluid to transfer a measured amount of sample fluid.